Decimal odds of 2.00 imply a 50% probability of winning. Odds of 1.50 imply 66.7%. Odds of 3.00 imply 33.3%. The formula is `1 / odds * 100`.
## Why this matters
If the bookmaker offers 2.00 on a coin flip, that’s a fair bet. If they offer 1.90, that’s the **margin** — your long-run loss. Every bookmaker book is built around margin.
## The two-way market test
Sum the implied probabilities of both sides:
– Tighter book: 102-104% (low margin)
– Average: 105-108%
– Bad book: 110%+
A 110% book is grinding you 10% per bet just to cover their costs. *Don’t bet there.*
## How sharps use this
1. Calculate the fair probability for each outcome (your model)
2. Convert each odd into implied probability
3. Bet only when your fair probability > implied + (margin / 2)
It’s not about “finding winners.” It’s about finding *prices that are wrong*.
## A quick mental shortcut
– 2.00 → 50%
– 1.50 → 67%
– 3.00 → 33%
– 1.91 → 52% (typical EU two-way line)
Keep these in your head. Once you can convert any odd to implied probability in two seconds, you’ll spot mispriced markets that 90% of recreational bettors miss.
